Chilling sensitivity of vegetables was investigated by means of Arrhenius equation of respiratory rate of whole and tissue slices or plugs, dehydrogenase activity of tissue slices and rate of potassium ion leakage from tissue slices.
1) Arrhenius plots of respiratory rate of chilling sensitive vegetables i. e. cucumber, eggplant and winter squash fruits, snap beans and sweet potato roots showed break points at the critical temperatures ranging from, 6.7°C to 10°C. These break points corresponded approximately with the critical temperatures for chilling injury of these vegetables. The Arrhenius plots showed different shapes for different species and cultivars of vegetables. Arrhenius plot of respiratory rate of potato tubers which is chilling-insensitive also showed a break point at nearly 10°C, giving a different shape of Arrhenius plot from those of chilling-sensitive vegetables.
2) Break points were observed at the critical temperatures in the Arrhenius plots of respiratory rate of tissue slices or plugs of chilling-sensitive vegetables i. e. cucumber and tomato (immature and ripe) fruits. Temperatures of break point corresponded approximately with the critical temperatures for chilling injury of these vegetables. The different shapes of Arrhenius plots were observed in the case of cucumber and tamato fruits. On the other hand Arrhenius plot of respiratory rate of tissue plugs of carrots (chilling-insensitive) showed a linear line, but that of radish roots (chilling-insensitive) showed a break point at a chilling temperature.
3) Arrhenius polts of dehydrogenase activity in tissue slices of sweet potato roots and potato tubers measured with the TTC.reagent showed break points at nearly 10°C. Arrhenius plot of dehydrogenase activity of potato tubers showed a marked change in the activity at the critical temperature in spite of chilling-insensitive.
4) Arrhenius plots of rate of potassium ion leakage from tissue slices of chilling-sensitive vegetables i. e. cucumber, eggplant, tomato and winter squash fruits, snap beans and sweet potato roots showed break points at chilling temperatures ranging from 6.7°C to 12.5°C. These temperatures at break corresponded approximately with the critical temperatures for chilling injury except winter squash fruit. Higher rates of potassium ion leakage were observed at lower temperatures below the break point. Arrhenius plots of rate of potassium ion leakage from tissue slices of potato tubers and radish roots (chilling-insensitive) showed break points at relatively high temperatures, and that of carrot roots (chilling-insensitive) showed a break point at a chilling temperature.

View full abstract

Changes in the contents of carbohydrates in pilei, stipes and bases of stipes of Hiratake-mushroom [Pleurotus ostreatus (Fr.) Qué∫] during post-harvest storage at six storage temperatures (-20, 0, 5, 10, 20 and 30°C) and freeze drying process were investigated. (1) The shelf life of Hiratake-mushroom was 18-22 days at 0°C, 12-13 days at 5°C, 6-8 days at 10°C 3-4 days at 20°C and 2-3 days at 30°C. (2) In this mushroom, arabitol, mannitol, trehalose, glucose and fructose were identified, and trehalose and mannitol were found to be major among them. During the post-harvest storage, the contents of each element decreased except mannitol. Especially the decrease in trehalose was marked, which shows that trehalose is a major respiratory substrate. The trehalose consumption at 0°C are much less than 5°C and the storage at the below 5°C turned out to be an effective way of storing. (3) The five polysaccharide fraction contents : formic acid-soluble fraction (R-glucan), alkali-soluble, acid-soluble fraction, hot alkali-soluble fraction, alkali-soluble, acid-insoluble fraction (S-glucan) and Chitin had no change during the post-harvest storage, and had a role of composing elements of cell wall. The acetic acid-soluble fraction content of the post-harvest storage decreased, and it was storage carbohydrate. (4) The contents of free sugars, free sugaralcohols and polysaccharides of Hiratake-mushroom during the freeze drying process had no change.

View full abstract

Storage temperature of shredded lettuce (5×5cm) vacuum-packed (200 mmHg) into Nylon/Poly-ethylene 60μm (NY/PE60) pouch during Practical distribution, such as refrigerator in processing Plant, delivery refrigerator truck and refrigerator at user's shop, was examined in summer season (atmospheric temperature : 22-32°C). Chemical, microbiological and organoleptic properties of shredded lettuce were investigated during storage at 1, 5, 10 and 20°C in laboratory scale, along with developing a simple cold delivery system using crushed ice, coolant and polystyrol container. The results were obtained as follows.
(1) In summer season, a series of temperature through the refrigerator in the processing plant, the refrigerator truck and the refrigerator at user's shop were 5-12°C. It was considered that the shelf life of shredded lettuce would be less than 3 days in this condition.
(2) The model investigation in laboratory scale suggested the storage stability of shredded lettuce was for 14 days at 1°C, for 5-7 days at 5°C, for 3-5 days at 10°C and for 1-3 days at 20°C, The deterioration factor was the ferment-like off-flavor formation. One of major components was ethyl alcohol, and the degree of ethyl alcohol formation enhanced with the increase of storage temperature.
(3) The preferable and simple delivery system was developed that the shredded lettuce (1kg×10 packages) pre-cooled to 1°C placed into polystyrol container with crushed ice 2kg. This system ex tended shelf life of shredded lettuce more than 5 days in atmospheric temperature : 20°C. It was showed that pre-cooling played an important role in practical delivery.

View full abstract